1. Field of the Invention
The present invention relates to pilot control relay valves. Even more particularly, the present invention relates to a pilot control relay valve employed to change the directional flow of fluids to a piston, valve or the like wherein controls provide a fluid signal to drive an end device such as a chemical injection pump to inject chemicals at a slow or rapid rate over a long period of time.
2. General Background of the Invention
Various devices are known which attempt to control a reciprocating pump. Devices of one such type are used in attempting to control a glycol pump which controls the level of liquid in a gas-liquid system and for circulating liquid in a gas-liquid system. These devices require a separate pump and pilot assembly such as that illustrated in U.S. Pat. No. 2,990,910, issued to G. O. Kimmell and entitled "Apparatus And Method For Circulating Controlling Liquids In Gas-Liquid Systems." Problems arise in the use of this type of system in that it simultaneously relieves pressure on the output or "low" side and increases pressure on the input or "high" side thereby preventing the pump from reaching a low speed or pumping rate.
Other pilot control relay valves rely on springs for the backstroke of the actuating piston in the pump which can lead to fatigue and breakdown.